Temperature indicating instrument



J. A. OBERMMER 2,072,312 TEMPERATURE iNDIcATING INSTRUMENT Filed July 28. 1954 V.2 sneetsnaex -1 EWR 'March. z,1937

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' jon a; O efmfuger v.1'. AQQB'ERMAIER 2,072,312 TEMPERATURE INDICATING INSTRUMENT Mardi-1937; i

Filed July 28, 1934 v v2 sheets-sheet 2 is neither thrown out of balance by short circuit cerned with devices Patented Mar. 42, 1937 PATENT orificev 2,072,312 TEMPERATURE mDIcA'rING msTRUMENr John A. Obermaier, Chicago, Application July 2s, 1934, serial No. 737,327

UNITED STA-Tas lClaim.

The present invention relates to temperature indicating instruments and is" particularly conf the type adapted to indicate the operating temperatures of water, oil, air, and/or exhaust gases of internal combustion engines,` such as Diesel enginesfor the like.

The efficient operation of such engines. de-

Y pends upon the proper distribution of the load among the several cylinders and proper combustion in each of the cylinders, and emcient operating conditions can only be maintained by means of adjustments effected after measuring the temperature conditions at various points.

One of the objects of theinvention is the provision of an improved temperature indicating instrument which is adapted to indicate accurately all of the various operating temperatures for the water, oil, air vand/or exhaust gases of such i an internal combustion engine.

lstrument of the class Anotherobject -of the. invention isthe provision oi an improved temperature indicating indescribed in which the manual operations required by the user are reduced to a minimum so-that there is less possidescribed in which all of throughout the several views.

bility of error in determination of temperatures.

Another object of the invention is the provision of an improved temperature indicating instrument of the class described which may be adapted both for automatic compensation of a cold end temperature of a thermo-couple or for the manual adjustment of the instrument so as to compensate for the variations in temperature of the cold end of the thermo-couple.

Another object is the provision of an improved temperature indicating instrument of the class fecting a measurement of a certain temperature are accomplished by a common switching device, so as to reduce the amount of manipulation necessary. i

Another object is the provision of the device of the class described in which the arrangement is such thatthe battery or source of electromotive force may be disconnected during the time the switching is being effected, so that the bridge nor by breaking the circuit while the battery is connected.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings in which similar characters of reference indicate similar parts Referring to the drawings, of which there are 5 -two sheets, Fig. 1 is a front elevational view of the connections for ef- I Fig. 5 is a fragmentary view of thesnap disc for the switch of Fig. 3; and

Fig. 6 is 'a fragmentary wiring diagram of a portion of a modification which is used in ccnnection with the rest of the diagram 'of Fig. 2 when the cold end compensator is to be adjusted manually.I

Referring to Fig. 1, |10 indicates in its entirety the electrical indicating instrument which is fundamentally a volt-meter or galvanometer and which is included in the circuit of Fig. 2. This instrument is preferably provided with the usual pointer II and dial l2, the dial having appropriate scale divisions and temperature indicia for the ranges o f temperatures to be measured. In the present case there are two ranges, zero to 1000 for measurement of exhaust gas `temperaurement of the water, oil, or air temperatures.

The adjusting screw i3 marked Z adjuster" is the u'sual zero adjustment screw the position of the needle IH by moving the fixed abutment of the spring which urges the needle to zero position. j,

The knob I4 controls a shaft which actuates a multiplicity of different switches, most of which are rotaryswitches for controlling the various connections of the heat responsive elements which have their changes in temperatureindicated on the galvanometer I 0. Knob i4 is provided with appropriate indicia, lsuch as the word Test which is used for test of the battery, Oil sump, Water inlet, Water outlet, Oil piston, "Oil cooler, and also @indicia for each of the exhaust temperatures for a number of cylinders, such as for example ten cylinders.

I5 indicates the knob of a rheostat used for adjustingv the battery voltage. screw for adjustment vof the resistance which compensates for the cold end 'temperature of the thermo-couples. VI1 indicates a push button used for cutting out the thermo-couples while 'the adjustment of the compensating resistance is made. The latter two members I6 and I 1 are,

which changes' ofcourse, only employed when the cold end adiustment is manual instead of automatic.

Referring to Fig. 2, indicates the galvanometer which is used as the indicator for all of the temperatures measured by the present device. For the purpose of measuring temperatures within the range of zero to 1000 degrees Fahrenheit, the device is preferably provided with a multiplicity of thermo-couples |8 to 29, inclusive.

10 Each of these thermo-couples consists of a pair of wires of dissimilar metals of suitable characteristics, so that an electromotive force is generated due to the diierence in temperature between the hot junction of the thermo-couple and the cold junction. The characteristics of these thermo-couples depend upon the specific temperatures to be measured.

The negative terminal 30 of galvanometer |0 may be'connected by conductor 3| to a calibrating resistance 32, which in turn is connected by conductor 33 to the switch arm 34. Switch arm 34 is adapted to wipe over the contacts 35 to 02, inclusive, in order to effect a proper connection for this terminal of the galvanometer to the other elements of the circui The first six contacts, to 40, may be joined together by a conductor 53, which'is connected to one end 54 of a bridge by conductor '55. The other twelve contacts, 4I to 52, are each connected by appropriate con- 30 ductors 56 to 61, inclusive, to the thermo-couples I8 to 23, inclusive. y

Where it is not desired to isolate these thermocouples completely, therotary selector switch 68 may be eliminated and connection made directly '35 from the opposite terminals of the thermo-couples |8A29 to conductor 69; in such case the connection would only be broken at one end of the thermo-couple.

In the present embodiment a rotary selector switch 68 is provided having a switch arm 10 and a multiplicity of contacts 1|. The last twelve of these contacts are connected by conductors 12, respectively, to the opposite terminals of the thermo-couples. The first six contacts would be de ad in this case.

The device is also preferably provided with a Wheatstone bridge having the fixed resistances 13, 14, 15, the junctions of the bridge being indicated at 13, 11, 5t, 18. A battery or constant 50 source of electromotive force 19 has one terminal connected by a conductor 80 to the junction 11. The opposite terminal of battery 18 is connected by conductor 8| through a battery rheostat 82 and battery switch 83 to the junc- 55 tion 18. The junction 16'of the bridge is connected by conductor 00 to the other terminal 85 of galvanometer i0.

The device is preferably provided with a multiplicity 'of thermo-bulbs Sii- 80, each bulb having a resistance which changes with a change of temperature. The Wheatstone bridge and galvanometer are, in eiiect, a device for measuring resistance for the determination of the thermobulb temperature, the instrument being calibrated in terms of temperature.

Inr order to `eiiect a test of the battery voltage; a battery ltest resistance 9| vis also includedfin the circuit and controlled by the'rotary selector switches, this resistance' being in `circuit when the knob |4 is set at test. One terminal ofeach of the resistances 30-9l is connected by the conductors 32--01, respectively, to the first six contacts 88 of the rotary selector switch 09. The other twelve iixed contacts of rotary selector switch 3l are joined by conductor |00 and connected by conductor |0| to the conductor 68 at |02.

Selector switch 99 has a rotating "switch arm |03 actuated by shaft |04, which is the common shaft controlled by knob |4 for actuating all of the selector switches.

Whenever it is not considered desirable to completely isolate the thermo-bulbs, the opposite terminal of the thermo-bulbs may be connected directly to the conductor |05, but when it is desired to completely isolate the thermo-bulbs, their opposite terminals may be connected by conductors |06| to the first six contacts of the rotary selector switch ||2. The switch arm ||3 is connected by an appropriate brush to a segment ||4, which is connected to conductor |05.v The lower twelve contacts of this selector switch may be joined together by conductor ||5 and connected by conductor ||6 to the opposite end of a cold end compensator resistance ||1. 'Ihis compensatorresistance may consist of a section of manganin resistance ||8 and a section ofnickel resistance H8, the variation in the resistance of the nickel being adapted to compensate for the variation in temperature of the cold ends of the thermo-couples.

The battery switch v83 is a switch ,operated by the same shaft |04 and is shown diagrammatically as a rotary switch, but-an ordinary rotary switch is not adapted to effect the battery switching with suilicient rapidity, and Figs. 3 to 5 show a switching arrangement which may be h employed'for switch 83.

Referring to Fig. 3, the shaft |04 preferably is provided with a snap disc |20 consisting of a metallic disc having a multiplicity of radial slots |2| in its periphery. The slots |2| are adapted to partially receive .a spring-pressed roller |22 which is carried by a plunger |23', and when the roller |22 is inslot |2| the switch arms 34, 10, |03 and ||3 are in registration with predetermined contacts. The shaft |04 is adapted to rotate the disc |20 with the switch arms, the rollerv |22 being cammed upwardly out of the slots |2| on the plane surface |24 of the disc switch arms register with another contact, when the roller |22 again drops into the slot. The disc and roller, in effect, comprise a snap arrange- 'ment for the rotary selector switches to retain the switches in registration with the contacts by which they are set in the present embodiment. The battery switch preferably comprises two switch elements |25, |26. The switch arm |25 is insulated from but mounted upon a rocking stirrup |21 upon which the roller |22 is mounted. A second roller |23 is rotatably mounted on stirrup |21 upon the opposite side of pivot |28. The roller |23 engages the plane surface of disc |20 at all times.

The plunger |23 with legs |20,y G30 at mounting thestirrup |21.

is bifurcated and provided its lower end for pivotally Switch arm |26 is in- I 20 until the- 'sulated from but iix'edly mounted on plunger |23' Plunger |23 is slidably mounted in the sleeve |3| and urged outwardly by compression of spring |32, and the complete plunger assembly is xedly mounted with respect to the rotation of the disc |20.

The operation of the battery switch 33 is as i'ollows: when the contacts of the selector switches 34, 10, |03,

| I3 are engaged by a switch arm, miler |22 is in slot |2I, the contacts |25, |20 are closed. As soon as the switch arms34..

10, |03, ||3 start to move away fromytliie central l Iposition of a xed contact,

` ward out of slot anzi The battery circuit lio 4 tery is disconnected and the irocking motion of stirrup |21 breaks contact between arms |25, |26.

Contact isbrken before the selector arms bridge between two adjacent contacts, so that the batb'eforethere is any short circuiting of two contacts or -inclusion of two thermo-couples or thermo-bulbsV in the circuit. is quickly closed again when therotary selector switch arms reach the center contact `position `of the next contact, thus the battery circuitisjis` always broken cluring'thev -switching operation A`so'that the bridge' is not` thrown out'of balance during the switching operations.v The galvanometer needle is neither thrown violently tothe right nor to the left and damage to the galvanometer is prevented. The battery circuit is quickly broken and quickly made, dueto vthe fact that the switch arms |25,

|26 .are of substantial length and the roller snaps into .and out of slots |2|.

Referring to Fig. 6, this'is ya modification shown by the fragment of a wiring diagram which may l `be substituted-for the lower portion of Fig. 2.

When it -is desired pensator manually,

to adjust the jcold end comthe` circuit of Fig. 6 may be employed. ."In thiscase the nickel section ||9rof the cold end compensator ||1is` provided with j an adjustable contact |33 .whichmay be actuated-by the Vadjustment screw I6.

f tor switch |34 may be 40 contact |35 of a double throw push'button switch,

` contacts |40.

Adjustable contact |33 is connected at |02 to the conductor |I. The opposite end of the cold end compensa- -tor is connected by conductorv |05 to bridge junction 18. While this manual adjustment of the cold end compensator is made, it isdesirable to-cut all of the thermo-couples out of the cir'- cuit so as toremove the indicator I0' from the inuence of the thermo-couples. Therefore, conductor 56 leading to the seventh contact on selec- `connected to the center thepush button being No. in Fig. 1. The rst thermo-couple is connected by conductor |36 to a -switch leaf contact'l3l. The common'lead |38 from the opposite end of all-of the thermo-couples is connected by conductor |39 to switch leaf `When the push button -is .pushed, the cold end compensator is connected. directly should, of course, be located close to the cold may then be adjusted by means of knob |-unti1 ill).` The thermo-couples Iii-29 are cut out of circuit b y the separation of the contacts |35, |31. -It should be understood that the cold junctions of the thermo-couples may be located wherever it is most economical to locate them.

Where the indicating instrument ,is at a great distance, thethermocouple wires are too expen- .slve to extend to the instrument, and in such junction may be located close to end of the junctions of the thermo-couples.

. The operation ofthe present indicating instrument is as follows: when it is'desired to check up the voltage'of the battery, the knob i4 is turned to the test position. The switch arm Awould then make contact with the rst contact of selector switch |03. The battery rheostat 32 the needle registers with the test mark shown is being made, all of button i1 is actuated to couples and the rheostat |33 adjusted by screwv and reading the temperatures an improved temperature and the temperature of measured onthe same indicating instrument as 30 back to the needle l0 through* at T in Figui on the d ial i2. While this test the thermo-couples and thermo-bulbs are out of circuit. When it is desired to adjust the cold end compensator, assuming the manual adjustment type is used, the cold junction temperature is iirst determined, theselector switches are set at test positions, push cut out the thermoi6 until the needle indicates this cold junction temperature on the dial; thereafter the temperatures of the engine may be measured at the various points on the indicator by merely turning the knob- I4 `to 'its respective positions on the dial.- The first six positions are, of course, read on the lower dial indicia, while the'higher temperatures of the last twelve positions are read on the upper dial indicia. Obviously, if an automatic cold end compensator is used, it is not necessary to' determine the cold end junction temperature.

' Itwill thus be observed that I have invented indicating instrument which is adapted to measure accurately temperatures throughout a wide range by means of the switching arrangements described. The instrument vis protected against excessive current water, oil or air may be calibrated in terms of temperature for indicating the temperature of said bulbs, a source of electrical energyv for energizing said instrument, switching means for controlling the connection of said bulbsto said switching means operable coincidentally with the rst mentioned'switching means for automatically disconnecting the source of electrical energy from said instrument during the major portion of. the movement of said first mentioned changes within the indicating instrument, and

switching means to prevent surges of current in said indicating means, during the switching operation, said second mentioned switching means comprlsing a rotatable member carried by a shaft controlling said first-mentioned switching means, said rotatable member having a plurality of slots provided with camming shou1ders,

and interengageable contacts resiliently mounted, one of said contacts being provided with a pair of camming rollers oppositely located with respect to the point of pivot of said latter contact, said rollers engaging said rotatable member in such manner that the contacts areA brought into engagement when one of said rollers engagesin one of said slots. 1

I, JOHN A. OBERMAIER. 

